what is the meaning LM in the tracking number?

Tarek, the combination of these two letters has no special meaning. You know, the tracking number is usually composed of four letters and nine numbers. Two letters start at the beginning and two letters (usually CN) ends. However, just single L means that your parcel was sent via EMS.

Thank you dear. and what is the time via EMS to delivered my parcel from China to Saudi arabia?

It takes 7 to 15 days.